Under National Fire Protection Association (NFPA), National Electrical Code (NEC), Underwriters Laboratories (UL) and local fire and building codes for each state, buildings that provide public access are required by law to have signs therein identifying the exits. These emergency signs are required to exhibit a specific amount of illumination and often times are required to have an emergency backup power source to provide emergency illumination to the exit sign for a specified period of time when electrical power to the building is interrupted to allow sufficient time for persons in the building to vacate.
Originally, an exit sign used standard incandescent lamps. The earliest alternatives to incandescent lamps were radioactive tritium gas and compact fluorescent lamps. In 1985, light-emitting diodes (LEDs) were introduced for use in exit signs. The most cost-effective alternative today over the exit signs that use incandescent lamps are LED exit signs. A standard LED exit sign generally uses only about 1 to 5 watts of power per surface. Because LEDs also last considerably longer than incandescent lamps, life cycle savings are dramatic.
There are currently several different types of LED exit signs available in the marketplace using a variety of LEDs in different configurations. There are a great number of LED sign manufacturers competing in the market. As a result, there is a wide range in price, quality, and energy consumption. Some LED signs use as few as 6 LEDs, others use 18 to 35 LEDs, and some use up to 200 LEDs. The rated energy consumption can thus range from as little as 1 watt up to 8 watts.
Architects, building owners, and many users desire to use recessed exit signs and/or other recessed emergency lighting devices to eliminate, or substantially reduce, visual lighting distractions on the ceiling, thereby having quiet ceilings. Conventional recessed exit signs include a recessed housing, an aluminum access plate that covers the opening in the ceiling and extends down from the surface of the ceiling, and a lens that is lighted through an edge using one or more LEDs.
When installing conventional recessed exit signs, the large housing is initially installed before ceiling drywall is installed. The ceiling drywall is then installed below the large housing, thereby forming a ceiling plane. A large hole is cut into the ceiling drywall that surrounds the profile of the housing so that the housing is accessible from below the ceiling plane. The lens and the associated lighting elements are coupled into the housing so that the lens extends below the ceiling plane. Additionally, the large aluminum access plate is installed below the ceiling drywall to cover up the hole and the large housing. The access plate also surrounds the top portion of the lens that extends below the ceiling drywall. The aluminum access plate is removable and allows installers and maintenance personnel to have access to the internal lighting components.
When viewing the conventional recessed exit signs from below the ceiling plane, the aluminum access plate, or cover plate, and the lens is visible. In fact, with the large silver access plate back-dropped by an expansive white or off-white ceilings the human eye is actually drawn towards the access plate, which is not aesthetically pleasing. Architects, building owners, and the many users using the conventional recessed exit signs would prefer having quieter ceilings with less object visible to the human eye, thus preferring to not have the access plate be visible.